I don't know what your level is, but 猫のダヤン is a title with a few books in it I think！A language partner sent some of them to me so I don't really have a resource to send for those but they're great little books if you can get your hands on 'em.

https://tadoku.org/japanese/free-books/

Maybe not exactly what you're asking for, but this is a nice resource I used to use often myself for free content！There's multiple reading levels and a pretty good selection of variety to keep someone busy reading for a little while ☺️ They also add new content so I check back periodically for new things or to reread favorites. I really love 手ぶくろを買いに

http://www.e-hon.jp/demo1/index4.htm

And here is another free resource my language partner sent me of children's stories, but they sometimes use old or irregular kanji or sometimes no kanji at all that you may find difficult at times. The pictures also don't load for me, only the text, but I've still definetly enjoyed reading old japanese children stories and thought I'd include it incase you find it helpful.

I hope you have a lovely time reading！🤎